Does Pulling Your T@B Overheat Your TV Tranny? (UPDATED)

RZRBUG

I tow with a 2012 GMC Sierra that has a heavy-duty tow package, including transmission cooler.  Twice, last year in the Big Horn Mountains and this year on the Million Dollar Highway, my transmission has gotten hot enough that I had to pull over and let it cool off.  There are several questions I have that maybe some of you could help with.

1) How hot can a transmission get and still operate safely?

2) Should you change your transmission fluid after it has gotten hot, if so, at what point?

3) Can you play with your gears and alleviate the problem?  My truck has a towing button (didn't seem to help) and a manual mode that allows me to force it to run and stay in gears 1-6.

4) After the transmission has gotten overheated, how is the best way to cool it down?  Shut everything off and let it sit, or put it in Park and let it idle?

I have done some research on the Internet and there is a myriad of opinions (surprise).  Just wondering if some of you have had experience with this situation.

jkjenn

Larry, do you have a transmission cooler installed? I had one installed shortly after purchasing my Jeep as I have heard it was a weak spot with my model.

Nomad

How do you tell if it's overheating? I have a manual tranny with a cooler and have never had an indication that something was hot. Temp gauge was always centered.

JandJ92010

Larry,  I just asked my step-son about your situation, he is a diesel mechanic. 1) 200*F is too hot. 180 is about normal. 2) Change the oil, filter, and have the tranny flushed. 4.) let it sit and idle to cool down. He also said that just towing a T@B should not over heat your truck anyway unless something is wrong with your tranny or the cool is plugged. Is the cooler plugged up? What rear end ratio do you have? Maybe it's too low. He said to take it to the dealer and tell them to "fix it", adding an auxiliary trans. cooler will help also. Good Luck.

JandJ92010

PXLated, That is why I love manual trannys, you don't have to worry about them like you do with automatics, they last forever.

Cyclonic

I've never had any issues with the tranny overheating either.

The tranny should range in temp between 140°-220°.  Manufactures usually put the fluid change at about every 100,000 miles, though they say it should be changed more often with heavy use conditions, like towing.  If it has turned a very dark red and smells burnt, you will want to have it changed.

You may be having a problem with the transmission cooler, and might want to think about getting it checked out if it seems to be overheating.

RZRBUG

Thanks everyone for the answers.  I know the temp of the tranny because I have a digital gauge that tells me the exact temp.  In both cases, I pulled over when the temp hit 205.  I will take it to the dealer as soon as I get the chance, although from what I've read, most of them don't have much of a clue, some even saying that up to 300 degrees is OK.  We'll see.

Jenn, the truck came with a tow package that includes auxiliary coolers, but there may be a problem with them.  In any case, I will have the fluid/filter changed, although the truck has just under 40,000 miles on it.

jkjenn

I did find that towing into a headwind at 100+ degree temps all day did raise my radiator temp. If I shut the a/c off for a few minutes (and opened the windows) the temp returned to normal, very quickly.

JandJ92010

Larry, just a thought, have you checked the calibration on the tranny temp gauge? Maybe it's reading high?  Or could you smell the tranny getting hot. With the tow pack you shouldn't have any problems.

RZRBUG

JandJ92010 said:

Larry, just a thought, have you checked the calibration on the tranny temp gauge? Maybe it's reading high?  Or could you smell the tranny getting hot. With the tow pack you shouldn't have any problems.

I haven't checked the calibration, but yeah, I could smell it when I stopped.  Plan a trip to the dealer as soon as I can get an appointment.  I'm not much of a mechanic and haven't checked for pinched lines, etc., but I did clean the fins.  I'm thinking there must be problem somewhere. Thanks.

RZRBUG

UPDATE:  Finally took the truck to the dealer today to have it checked out.  The assessment was that the transmission was operating normally.  He said the fluid was red and clean and looked good.

Following is some information from a GM printout they gave me about temperature operating ranges. Disclaimer:  This pertains to my 2012 GMC Sierra and may not apply to any other tow vehicle.  If you suspect you have a problem, you should take it to your dealer (if under warranty) or to a reputable mechanic.

1.  Normal operating temperature between 160*F to 200*F.  (Mine reached 205*F before I pulled over to let it cool.)

2.  The following transmission-related indicators and messages may be displayed on the Instrument Panel Cluster (IPC).

  A: "TRANSMISSION HOT IDLE ENGINE"  This message is displayed when the TCM detects a transmission fluid temperature equal to or greater than 270*F for 5 seconds. (I take this to mean there should be no real concern until it hits 270*F, although I will never let it get that high if I know it.)

  B: "SERVICE TRANSMISSION"  This message displays when there is a problem with the transmission.

The head of the service department basically told me not to worry about it.  He said that if anything was wrong I would know it because the IPC would tell me.

So, some peace of mind at least.  And, I now have a record of informing them of what I perceived to be a problem before the warranty is out.

RZRBUG

Sandra said:

You weren't towing in the mountains with the cruise control on by any chance?

Absolutely not.  And, the Sierra heavy-duty tow package has a tow button, which I was using, that prevents excessive upshifting and downshifting.  I think it may be a quirk in the design as I overheard one of the mechanics tell another that he had just talked to another customer who had the same questions I did.

Next time I do some uphill towing I may let it go a little longer just to see how far it will go, stopping before it gets to the limits mentioned in the literature.

dinzzy

I know this is an old post and you my have this all dialed in now.  On my 2016 Tacoma I have installed a Scan Gauge II into the OBD II port under the dash.  It monitors many things including trans torque converter temp as well as trans fluid temperature and coolant temp. I have used this Gauge to modify how I drive and gear selection.  I tow in S4 (gear) which is a 1/1 ratio to the engine.  I have had no issues with over heating even when traveling to Sedona in 108 degree heat last summer. I did turn off the A/C on one long uphill grade.  I watch the Gauge and adjusted my driving.